I've used the Harbor Freight Carpet cutting blades for almost 2 yrs now...only problem I've had with them was my own fault...I put two in at once I forgot they clung so heavinly together....they fit my Olfa cutters just fine and at the savings I've had with them I no longer think I should hold onto a blade a bit longer when they do dull a bit..I save them to go into my paper cutters for double duty. I love the savings and the ideas and suggestions of the board.